Regulation of stress granule formation in human oligodendrocytes

Oligodendrocyte (OL) injury and subsequent loss is a pathologic hallmark of multiple sclerosis (MS). Stress granules (SGs) are membrane-less organelles containing mRNAs stalled in translation and considered as participants of the cellular response to stress. Here we show SGs in OLs in active and inactive areas of MS lesions as well as in normal-appearing white matter. In cultures of primary human adult brain derived OLs, metabolic stress conditions induce transient SG formation in these cells. Combining pro-inflammatory cytokines, which alone do not induce SG formation, with metabolic stress results in persistence of SGs. Unlike sodium arsenite, metabolic stress induced SG formation is not blocked by the integrated stress response inhibitor. Glycolytic inhibition also induces persistent SGs indicating the dependence of SG formation and disassembly on the energetic glycolytic properties of human OLs. We conclude that SG persistence in OLs in MS reflects their response to a combination of metabolic stress and pro-inflammatory conditions.

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Florian Pernin
Jan 24, 2024 Bulk RNAseq was performed at at the Génome Québec Centre using the Illumina platform and NovaSeq 6000 PE100 machine Bulk sequencing -We We used the GenPipes workflow for alignment to to the GRCh38 human genome and read counting.Raw FastQ files were aligned to to the GRCh38 genome reference using the STAR aligner with default parameters.Raw reads were quantified using HTSeq count.Raw read counts were then normalized and variance-stabilized.DESeq2 package in in R was employed for further analysis.Significantly differentially expressed genes were filtered using a p-value cutoff of of <0.05.Heatmaps were generated after clustering using the Hierarchical Clustering Image function in in GenePattern (v3.9.11).Gene clustering was performed using Pearson correlation and the normalized values were transformed using a long transformation.Finally, row normalization was applied for the final visualization.
Single nuclear RNA sequencing -The snRNAseq data of of human MS MS and control patients were obtained from Schirmer, Jakel and Absinta datasets.The datasets were subjected to to the standard Seurat pipeline for dimensionality reduction, cell type identification, gene expression normalization, and clustering.OL OL clusters were chosen in in each dataset using canonical OL OL markers and information provided by by the reference publications.Average expression and differentially expressed genes (DEG) between MS MS and control OLs were identified using a log2 (fold change) > 0.25 and an an adjusted p-value < 0.05 as as cutoffs.The log2FC and adjusted p-values were utilized to to generate a bubble plot using ggplot2 v3.3.6 in in R. R. A Venn diagram was employed to to visualize the overlap between significant genes in in the edge of of chronic active and the edge of of chronic inactive lesions using the Venny 2.1 web tool.